Tube squaring machines are required to precision cut a square surface at the end of a tube such that, a precision weld can be made for attachment of the end thereof. In many cases, a tube must be cut to an exact length, with the ends of the tube being square.
Existing squaring machines grip the end of the tube in a collet after which a machine tool is adjustably fed against the end of the tube to remove metal and leave the end square. Existing squaring machines, however, do not have a means of precision indexing the feed of the tool, and therefore the feed of such machines cannot be adjusted to remove a predetermined amount of metal. An operator will frequently perform a series of machining operations, each time machining off a small portion of the metal of the tube, removing the tube from the machine to measure its length and then machine off more metal until the desired length of the tube has been reached. If care is not exercised, too much metal may be removed and the piece rendered useless.
In existing squaring machines, the feed is controlled by a handle which is rotated and operates a cam that moves the tool against the end of a work piece. Such cam operated feeds do not provide a linear relationship between the advancement of the feed and the angle of the handle. As a result, an operator cannot determine the distance the feed has advanced by the angle through which the handle is rotated.
Furthermore, to cut a square end to a piece of tubing, the machine must attach to the end of the tubing so as to retain the tubing with the axis thereof coaxial with the axis of the drive shaft of the cutting tool. If the axis of the tubing is at an angle relative to the axis of .the squaring machine, the machine will cut an end having a plane which will be angled, and not perpendicular to the length of the tube. A collet at the end of the machine is provided to clamp the end of the tube in the desired position.
Most existing collets are made of .metal, and are tubular in shape with a number of longitudinal cuts extending from alternate ends of the tubular collet. A work piece of tubing is then fitted into the interior of the collet and the collet fitted into a tapered retainer in the housing of the tool, and held in place by a complementary tapered nut. Tightening of the nut compresses the collet and retains the work piece.
It has been found that it is difficult to insert a length of metal tubing into a metal collet because the diameter of the inner bore of the collet is nearly equal to the outer diameter of the work piece to be inserted therein. Furthermore, existing metal collets may damage surfaces of a work piece on which a highly polished surface is required.
Existing metal collets also permit very little expansion of the inner diameter from the compressed position in which the collet is locked against the outer surface of the work piece, and the relief position when the work piece can be removed from the collet.
It would, therefore, be desirable to provide a squaring machine for which the feed can be accurately measured and controlled. Also, it would be desirable to provide a collet for a tube squaring machine which will not mar the finish of a polished tubing, can be easily used, and will firmly grip and retain a work piece within the machine.